This invention concerns track laying tractors of the type comprising a tractor body having a framework supported laterally by a pair of track units, a crane placed upon one of the sides of the tractor body and having a movable boom which can be tilted laterally and pivoted at the base on an appendage fixed to the outer face of the adjacent track unit, a counterweight for balancing the load, placed on the side of the tractor body opposite to the crame, and an additional framework which supports means for varying the lateral tilt of the crane, means for adjusting the position of the counterweight and means for lifting the load.
In tractors of this type there is the problem of making an additional framework which shall be capable of supporting the considerable stresses arising from maneuvering of the useful load and of the counterweight and that, at the same time, will itself have the smallest possible mass.
According to known methods, this additional framework consists of two arched structures each of which is arranged in correspondence with a track unit and curves round the upper portion of the said track unit so as to rest, on the inside, upon the supporting structure of the tractor, and on the outside, upon an appendage fixed to the outer side of the track frame.
This solution has the disadvantage that one section of each of the two arched structures projects laterally from the outer edge of the associated track unit. Since it is necessary to transport the tractor from one place to another, it is necessary, in certain cases in order to reduce the transverse dimension of the tractor, to dismantle the two arched structures, and, consequently, all the members which these support.